Perhaps no sports figure was responsible for thrilling, or disappointing, more sports fans than Marvin Miller, the legendary baseball union chief who died of liver cancer, at 95, Tuesday morning. When your favorite team signs a big-name free agent, giving you hope during the dreary off-season? Thank Miller. Your favorite player ditches town for an even fatter contract? Well, you can blame Miller too.

In December of 1975, Major League Baseball became the first major U.S. sports league to adopt free agency, thanks largely to Miller’s efforts. On the open market, player salaries exploded, as did overall revenues. As the Associated Press reports, “MLB’s revenue has grown from $50 million in 1967 to $7.5 billion this year.” Other leagues eventually followed suit. Former commissioner Fay Vincent told the AP:

“I think he’s the most important baseball figure of the last 50 years.He changed not just the sport but the business of the sport permanently, and he truly emancipated the baseball player – and in the process all professional athletes. Prior to his time, they had few rights; at the moment, they control the games.”

Miller was a tireless advocate for the rights of players. He led three strikes; most notably, seven weeks of the 1981 season were cancelled. Even as recently as last year, when baseball and its union started embarking on a new collective bargaining that was signed without any of the rancor we have recently seen in recent NBA, NHL, and NFL negotiations, Miller — who retired from the union in ’82 — criticized baseball’s union leaders for agreeing to increased steroid testing. As TIME reported:

For years, the union resisted testing; in 2002, the players finally agreed to a relatively weak program. But as the steroid scandal boomed, public pressure, including exhortations from Congress, compelled the players and owners to amend the agreement several times in order to create both stronger protocols and harsher penalties for offenders. Legendary baseball labor leader Marvin Miller, who helped the players win free agency back in the 1970s, is still critical of the union’s decision to revise these agreements before they expired. “That’s not realistic behavior for a union,” Miller tells TIME. (The Major League Baseball Players Association, or MLBPA, declines to respond to Miller’s comments).

Miller didn’t work for the fans. Steroid testing is clearly a positive development, strikes stink, and free agency has helped create payroll disparities that hamstring small-market teams. But even if you don’t love how Miller pioneered the era of sports as a billion dollar business, you can’t deny his impact.

Somehow, Miller is not in baseball’s Hall of Fame, a black mark on that institution. But with or without the plaque, Miller altered sports forever.